BLM LIBRARY 88016320 T-N-239 TECHNICAL NOTE Bureau of Land Management U.S. DEPARTMENT OF THE INTERIOR HABITAT MANAGEMENT SERIES FOR UNIQUE OR ENDANGERED SPECIES by Carol Snow, Research Biologist Conservation Library Denver Public Library Report No. 7 Golden Eagle Aquila chrysaetos QL 84.2 .L35 no. 239 c.2 Bureau of Land Management Library Center4 lg 50, Denver Federal Denver, CO 80225 ^ i/tffYfZ' -33b .^SS^^^ FOREWORD This Technical Note series on wildlife is designed to provide a literature review and summary of current knowledge pertaining to endangered and other wildlife species occurring on public lands. We in the Bureau of Land Management have recognized the need for basic wildlife information in order to do an effective job in land-use planning. Sound planning must identify the negative aspects as well as the positive benefits of any proposed land management decision or program. It is our hope, too, that this series will also prove useful to others —be they land managers, students, researchers or interested citizens. Director Bureau of Land Management Department of the Interior Bureau of Land Management BIdg. 50, Denver Federal Center Denver, CO 80225 TABLE OF CONTENTS Page Species Description 1 Distribution h Status and Population Trend 8 Life History 9 Food Habits . « 9 Rabbits and Rodents 9 Game Species 10 Carrion 11 Livestock 12 Characteristics of Eagle Kills Ik Hunting Methods 16 Weight-lifting Abilities 17 Food Requirements 18 Density . „ 20 Courtship 21 Alternate Nests 21 Nest Defense 22 Clutch Size 22 Incubation 22 Parental Behavior 23 Eaglet Behavior 23 Fledging 23 Movements 23 Interspecies Relationships 2k Vocalizations 2k Productivity 2$ Mortality „ . 27 Impact Injuries 27 Shooting 27 Electrocution 27 Chemical Contamination .0 29 Organochlorine pesticides 29 Mercury 31 Dieldrin 32 Habitat Requirements 32 Cliffs and Trees „ 32 Nest Size „ 33 Direction of Nest Exposure 33 Alternate Nests 3k Tolerance of Human Activity 35 TABLE OF CONTENTS (Cont'd) Page Protective Measures Instituted 35 Legal or Regulatory 35 Captive Rearing 36 Habitat Protection and Improvement 36 Re introduction 37 Species and Habitat Management Recommendations ... 37 Ongoing Research Projects » ... 39 Summary 1+1 Authorities „ „ „ . 1+2 Governmental, Private and Internat'l Organizations Actively Involved with This Species' Welfare. 1+3 Literature Cited 1+6 Additional References „ „ 52 Introduction The objective of this report is to provide BIM personnel with the latest and most up-to-date information on rare or endangered species occurring on the public domain. This will provide a tool for improved understanding of the interrelationships between the species and its environment and encourage an end product of enlightened land management which will fully consider the species' welfare in all management decisions. 1. Species Description The golden eagle is widely distributed throughout the northern hemisphere. Eight races have been described, but only Aquila chrysaetos canadensis is found in North America. In medieval Europe, the golden eagle was flown only by kings. In many North American Indian cultures, the golden eagle is the Thunderbird, who is variously credited with the creation of the world, is a messenger of the gods, or is the Great Spirit himself. To this day eagles and eagle feathers are highly valued by many Indian tribes and are important parts of many ceremonies (Bent, 1937', Grossman and Hamlet, I96I4). Feathers which are collected from accidentally killed eagles or confis- cated by federal agents are often given to Indians for religious and ceremonial purposes. Common vernacular names for the golden eagle include brown eagle, calumet eagle, ring-tailed eagle, black eagle, mountain eagle, royal eagle, war eagle, dark eagle, and black Mexican eagle. The wing span may extend from six to seven and one -half feet. The weight of mature adults varies from eight to over twelve pounds. Females are larger than males (Jollie, 19h3> Kalmbach et al, 1961i; Brown and Amadon, 1968). Newly hatched eaglets are covered with short, thick, dirty- white down which is replaced with a longer, thicker pure white down. As the black feathers of the juvenile plumage begin to replace the down along certain feather tracts, there is a characteristic "black and white" phase which is apparent at about six to seven weeks of age (Murphy, 1973b). At eight weeks of age, eaglets are fully feathered. They are ready to fledge at an average age of ten weeks (Bent, 1937). A newly fledged golden eagle has a very distinctive plumage. It is considerably darker than the adult and is blackish-brown in appearance. The crown and hackles are darker and duller. The basal one third of the feathers on the back and the basal half of the breast feathers are white. There is a broad terminal band of brownish black on the tail feathers which covers about one fourth of the central rectrices and graduates , up to approximately one half of the outer feathers. The remaining portion of the tail feathers is white. The long wing feathers are blackish with much white near the bases of the inner primaries and all the secondaries. This pattern forms a conspicuous white patch at the carpal joint of the wing which is called a "wrist patch" or a "mirror" (Bent, 1937; Brown and Amadon, 1968). This "mirror" is also visible from above (Kochert, personal communication ; Nelson, personal communication). Newly-fledged eaglets are as large and as heavy as or heavier than adults (Murphy, 1973b). See Figure 2. Adult plumage is attained over a period of three to four years and involves a gradual reduction of the amount of white at the base of the feathers. During the second year, the tail feathers have dark brown tips and are mottled with grayish brown about halfway up the vane. The middle two rectrices are completely mottled (Kochert, 1973c). At three years of age a golden eagle may still have white patches at the bases of some of its tail feathers and in some of the body plumage. The white areas in the wings gradually disappear (Bent, 1937; Brown and Amadon, 1968; Grossman and Hamlet, 196U; Jollie , 19h3 19U7). The golden eagle is named for the lanceolate feathers on the crown of the head and the nape of its neck which are tipped and edged with a tawny or golden-buff color. These hackles pro- duce a golden cast against the otherwise sepia to dark brown plumage. The tail of the adult is more or less indistinctly and irregularly barred or spotted with dark gray or brown and has broad blackish tips. The wing feathers are brownish-black with varying amounts of white and gray mottling forming indistinct basal bands. There is little or no white in the body feathers. The feathering on the tarsi is slightly paler than on the rest of the body, and the underside tends to be paler than the upper side (Brown and Amadon, 1968; Grossman and Hamlet, I96I4; Jollie, 19l7; Bent, 1937). See Figure 2. Jollie (19U7) gives very detailed descriptions of plumage changes in the golden eagle. Some observers have described plumages for juvenile, immature and adult birds. In this re- port only the terms juvenile and adult are used, with juvenile referring to all birds that are not yet in adult plumage. Field identification may be difficult in areas where juvenile bald eagles ( Haliaeetus leucocephalus ) and turkey vultures ( Cathartes aura ) are also found. Golden eagles have fully feathered tarsi, whereas bald eagles and turkey vultures do not, but this characteristic is useful for identification only at close range. Juvenile golden eagles are usually distinguish- able from adults by the large white tail base and the white wing patches. At close range adult golden eagles can be identi- fied by the golden hackles which are also visible through good binoculars. 2-3 At a distance, eagles and vultures may appear similar, but flight patterns are different. The turkey vulture holds its wings in a dihedral and tends to soar more frequently than the golden eagle, with a somewhat rocking motion. The golden eagle's wings are held nearly horizontal when it is soaring. The coverts on the undersurfaces of the wings of the turkey vulture appear very dark, while the undersurfaces of the pri- maries and secondaries appear much lighter and gray-toned. It also has a small head and long narrow tail compared to the golden eagle. It does not have white on any part of its body, as does the juvenile golden eagle. See Figure l. Distinctions between juvenile bald eagles and golden eagles are more nebulous. Juvenile bald eagles have variably marked gray-mottled or white -mottled tail feathers which are gradually replaced with white tail feathers. The underwing coverts are mottled with white, but they do not form white wing patches. Another useful field characteristic to distinguish juvenile bald eagles from golden eagles is the strong contrast between the brownish plumage of the breast and abdomen and the gray- mottled appearance of the underwing coverts on the bald eagle (Murphy, 1973b). Adult golden eagles have dark underwing coverts and a dark-tipped tail marked with irregular brown bars at the base. See Figure 2. Both adult and juvenile golden eagles have brown eyes, as does the juvenile bald eagle up to the age of four. Golden eagles have black beaks, yellow ceres, yellow toes and black claws. Juvenile bald eagles tend to have brownish beaks and grayish- yellow ceres, although the beaks of first-year bald eagles may be grayish black (Jollie, 191x3 > Bent, 1937 ; Brown and Amadon, 1968; Grossman and Hamlet, 196U; Sprunt, 1973; Robards, 1973). 2. Distribution, Present and Former Aquila chrysaetos canadensis is found from northern Alaska in the Brooks Range, British Columbia, Mackenzie, northern Saskatchewan, northern Manitoba and Quebec, and the Gaspe Peninsula south to northern Baja California, Sonora, Sinaloa, Durango, Guanajuato, Nuevo Leon, west Texas (Brewster County), western Oklahoma, western Nebraska, western South Dakota, eastern Montana, northern Ontario across to New York, northern New Hampshire and Maine (A.O.U.